I've heard them as long as I can remember...and no, I've never discussed this with a therapist.  

Let me explain:  Music has shaped my entire life and I was fortunate to be able to turn that into a totally fulfilling career...with one exception...those voices.  From the time I heard and understood my first song, I had to sing along.  The first singers that I emulated were the pop singers and there were some great ones.  When I sang along with Frank Sinatra, the voice in my head sounded just like him.  Tony Bennett, Perry Como, Nat King Cole, Dean Martin, Andy Williams...yep, nailed them, although some of those "crooners" had a lot more deceptive vocal ranges than it appeared.  Rock and Roll was an abrupt style change but I could sing Elvis as well as anyone.  It was just a different voice...same head. When I really started to like R&B, it really stretched this white boy to change those voices to Chuck Berry, Little Richard, James Brown, Ray Charles or Fats Domino.  


When I went to L.A. to seek fame and fortune, I took this cacophony of voices with me.  Alas, when I started recording, the sad truth was revealed to me.  I had sung along with the masters and gained this inner soul, which was a good thing because music had shifted to a more soulful sound. In those first recording sessions, I nailed those songs.  On the playbacks, I fully expected to hear Stevie Wonder, Smokey Robinson or maybe even a little Bill Medley.  What I got was a bad Andy Williams or Pat Boone (although, that might be an oxymoron).  Sadly, the voices in my head were not connected to my mouth.  Which explains how I made my living on the production side of the business.
Now admit it.  When you sing along, you sound like that artist in your head...right!  I did play this fantasy game over the years, though.  If I were a famous singer, whose voice would I want?  It changed a few times.  In the early days (when I was white) I always thought that Andy Williams could handle almost any pop song and sing it well.  Everyone wanted to be Elvis, but I would have been happy as Rick Nelson.  Later, I thought that I could handle a writer/artist sound like James Taylor.  But truth be known, I would have given all to sing R&B.  Something about the dynamics of soul and music...but that was outside the realm of white artists at the time.  


The other day my wife asked me who I would like to sing like now if I had the choice.  It's interesting because the voice I seem to hear in my head most often is Michael McDonald.  He's the white singer with soul that I tried to be from the beginning of my career.  Co-incidentally, we're going to see him at the Golden State Theater in Monterey on August 3rd.  Don't know how exciting it will be, though.  I'm sure he'll sound a lot like me.